Pothole
is a kind of fluvial feature found on the river bed in upper course. They
can be seen in dry season.

Large
boulders are commonly found on the river beds of the upper courses of
rivers. Therefore, the ruggedness of the river bed is high over there. The
flow of water is affected and eddies are commonly found. Eddies with
gravels put strong abrasion on river bed. Circular grinding will
eventually create round holes on river bed.

The
mouth of a pothole is usually smaller than the inner part because gravels
entering the pothole can hardly coming out again. The abrasion inside the
pothole is therefore greater.